Commercial aircraft typically employ an environmental control system to pressurize a passenger cabin of the aircraft and/or thermal anti-icing systems to provide heated air for anti-icing applications. Air supply is typically provided to these systems by bleed air extracted from or provided by a compressor of an aircraft engine. To meet the pressure and/or temperature demands of the various aircraft systems, bleed air is often extracted from a higher stage of the compressor that provides bleed air having a pressure and/or temperature above that demanded by the various systems. For example, bleed air is often extracted from a mid-stage of a high pressure compressor of an aircraft engine. The pressurized bleed air is then often cooled, via a precooler, and reduced in pressure, via a pressure regulating valve, prior to providing the bleed air to a system (e.g., an environmental control system) of the aircraft. Therefore, much of the energy spent by the engine to produce the bleed air is wasted when cooling the bleed air and/or reducing the pressure of the bleed air and, thus, extracting high-pressure bleed air in such a manner may reduce the efficiency of the engine.
To reduce extraction of bleed air, some known systems employ a turbo-compressor that receives ambient air from an atmospheric inlet. The turbo-compressor pressurizes the ambient air prior to supplying the various aircraft systems. However, the atmospheric inlet produces drag. Additionally, the atmospheric inlet is often susceptible to icing and, thus, requires an anti-icing system that increases costs and system complexity. Further, the compressor may have to be relatively large to produce a pressure change sufficient to power the systems of an aircraft. Some known piston engines provide pressurized air for an aircraft cabin environmental control system with a shaft-driven compressor, typically known as a supercharger. Known shaft-driven superchargers also receive ambient air from an atmospheric inlet and, thus, also suffer from the above-identified drawbacks.